This view of the twilight sky and Martian horizon taken by NASA's Curiosity Mars rover includes Earth as the brightest point of light in the night sky. Earth is a little left of center in the image, and our moon is just below Earth.

This frame from an animation from NASA's Mars rover Curiosity shows the rover drilling into rock target 'Cumberland.' The drilling was performed during the 279th Martian day, or sol, of the Curiosity's work on Mars (May 19, 2013).

This image from the Mars Hand Lens Imager on NASA's Mars rover Curiosity shows the patch of rock cleaned by the first use of the rover's Dust Removal Tool (DRT). The tool is a motorized, wire-bristle brush on the turret at the end of the rover's arm.

The two bodies in this portion of an evening-sky view by NASA's Mars rover Curiosity are Earth and Earth's moon. The rover's Mast Camera (Mastcam) imaged them in the twilight sky of Curiosity's 529th Martian day, or sol (Jan. 31, 2014).

One type of feature of scientific interest on the mountain inside Gale crater is exposure of cemented fractures, evidence that groundwater once reached to at least that height of the mountain. This image is from NASA's Mars Reconnaissance Orbiter.

This oblique view of the mound in Gale crater shows several different rock types of interest to the Mars Science Laboratory mission. The Mars Science Laboratory rover, Curiosity, will use its full instrument suite to study these minerals and how they form

Mars scientists have several important hypotheses about how these minerals may reflect changes in the amount of water on the surface of Mars. The Mars Science Laboratory rover, Curiosity, will use its full suite of instruments to study these minerals.

This oblique view of Gale crater shows the landing site and the mound of layered rocks that NASA's Mars Science Laboratory will investigate. The landing site is in the smooth area in front of the mound.

This oblique view of Gale crater shows the landing site and the mound of layered rocks that NASA's Mars Science Laboratory will investigate. The landing site is in the smooth area in front of the mound.

This oblique, southward-looking view of Gale crater shows the mound of layered rocks that NASA's Mars Science Laboratory will investigate. The mission's selected landing site is just north of the mound inside the crater.

This computer-generated view depicts part of Mars at the boundary between darkness and daylight, with an area including Gale Crater beginning to catch morning light. NASA has selected Gale as the landing site for the Mars Science Laboratory mission.

This computer-generated view based on multiple orbital observations shows Mars' Gale crater as if seen from an aircraft northwest of the crater. NASA has selected Gale as the landing site for the Mars Science Laboratory mission.

A NASA Dryden Flight Research Center F/A-18 852 aircraft makes a 40-degree dive during June 2011 flight tests of a Mars landing radar. A test model of the landing radar for NASA's Mars Science Laboratory mission is inside a pod under the left wing.

A NASA Dryden Flight Research Center F/A-18 852 aircraft performs a roll during June 2011 flight tests of a Mars landing radar. A test model of the landing radar for NASA's Mars Science Laboratory mission is inside a pod under the aircraft's left wing.

This photograph of the NASA Mars Science Laboratory rover, Curiosity, was taken during testing on June 3, 2011. The turret at the end of Curiosity's robotic arm holds five devices. In this view, the drill is at the six o'clock position.

This photograph of the NASA Mars Science Laboratory rover, Curiosity, was taken during mobility testing on June 3, 2011. The location is inside the Spacecraft Assembly Facility at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

This photograph of the NASA Mars Science Laboratory rover, Curiosity, was taken during mobility testing on June 3, 2011. The location is inside the Spacecraft Assembly Facility at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

This photograph of the NASA Mars Science Laboratory rover, Curiosity, was taken during mobility testing on June 3, 2011. The location is inside the Spacecraft Assembly Facility at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

This photograph of the NASA Mars Science Laboratory rover, Curiosity, was taken during mobility testing on June 3, 2011. The location is inside the Spacecraft Assembly Facility at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

This photograph of the NASA Mars Science Laboratory rover, Curiosity, was taken during mobility testing on June 3, 2011. The location is inside the Spacecraft Assembly Facility at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

NASA's Mars rover Curiosity took the images combined into this mosaic of the rover's upper deck. The images were taken in March 2011. At the time, Curiosity was inside a space simulation chamber at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

This artist concept features NASA's Mars Science Laboratory Curiosity rover, a mobile robot for investigating Mars' past or present ability to sustain microbial life. Curiosity is being tested in preparation for launch in the fall of 2011.